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Breath Testing

Breath testing uses the measurement of hydrogen and methane in the breath to diagnose several conditions that cause gastrointestinal symptoms. In humans, only bacteria - specifically, anaerobic bacteria in the colon - are capable of producing hydrogen and methane. The bacteria produces hydrogen and methane when they are exposed to unabsorbed food, particularly sugars and carbohydrates. Although limited hydrogen and methane is produced from the small amounts of unabsorbed food that normally reach the colon, large amounts may be produced when there is a problem with the digestion or absorption of food in the small intestine, that allows more unabsorbed food to reach the colon.

Large amounts of hydrogen also may be produced when the colon bacteria move back into the small intestine, a condition called bacterial overgrowth of the small bowel. In this latter instance, the bacteria are exposed to unabsorbed food that has not had a chance to completely traverse the small intestine to be fully digested and absorbed. Some of the hydrogen and methane produced by the bacteria, whether in the small intestine or the colon, is absorbed into the blood flowing through the wall of the small intestine and colon. The hydrogen-containing blood travels to the lungs where the hydrogen is released and exhaled in the breath where it can be measured.

Other conditions that are tested for include lactose and fructose intolerance. Lactose intolerance is an inability to digest and absorb lactose (the sugar in milk) that results in gastrointestinal symptoms when milk or products containing milk are drunk or eaten. Fructose symptoms are similar. Fructose is found in many sweetened products.